Implantable stimulation devices deliver electrical stimuli to nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators to treat motor and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder subluxation, etc. The description that follows will generally focus on the use of the invention within a Spinal Cord Stimulation (SCS) system, such as that disclosed in U.S. Pat. No. 6,516,227. However, the present invention may find applicability with any implantable medical device or in any implantable medical device system.
An SCS system typically includes an Implantable Pulse Generator (IPG), whose structure and construction is further described in U.S. Provisional Patent Application No. 61/874,194, entitled “Construction for an Implantable Medical Device Employing an Internal Support Structure,” filed Sep. 5, 2013, which is incorporated herein by reference in its entirety. The IPG 10 of the '194 Application is shown in FIG. 1, which includes a biocompatible device case 30 that holds the circuitry and battery 34 (FIG. 2) necessary for the IPG to function. The IPG 10 is coupled to electrodes 16 via one or more electrode leads 14 that form an electrode array 12. The electrodes 16 are carried on a flexible body 18, which also houses the individual signal wires 20 coupled to each electrode 16. The signal wires 20 are also coupled to proximal contacts 22, which are insertable into lead connectors 24 fixed in a header 28 on the IPG 10, which header can comprise an epoxy for example. Once inserted, the proximal contacts 22 connect to header contacts 26 in the lead connectors 24, which header contacts 26 are in turn coupled by feedthrough pins 48 to circuitry within the case 30 as will be explained subsequently. In the illustrated embodiment, there are sixteen electrodes 16 (E1-E16) split between two leads 14, although the number of leads and electrodes is application specific and therefore can vary. In a SCS application, electrode leads 14 are typically implanted on the right and left side of the dura within the patient's spinal cord. The proximal electrodes are then tunneled through the patient's tissue to a distant location, such as the buttocks, where the IPG case 30 is implanted, at which point they are coupled to the lead connectors 24.
FIG. 2 shows perspective bottom and top sides of the IPG 10 with the case 30 removed so that internal components can be seen. In particular, a battery 34, communication coil 40, and a printed circuit board (PCB) 42, can be seen. As explained in the '194 Application, these components are affixed to and integrated using a rigid (e.g., plastic) support structure 38. Battery 34 in this example is a permanent, non-wirelessly-rechargeable battery. (Battery 34 could also be rechargeable, in which case either coil 40 or another recharging coil would be used to wirelessly receive a charging field that is rectified to charge the battery 34). The communication coil 40 enables communication between the IPG 10 and a device external to the patient (not shown), thus allowing bidirectional communication to occur by magnetic induction. The ends of coil 40 are soldered to coil pins 44 molded into the support structure 38 to facilitate the coil 40's eventual connection to circuitry on the IPG PCB 42. IPG PCB 42 integrates the various circuits and electronics needed for operation of the IPG 10. As shown in FIG. 2, coil 40 is proximate to the bottom side of the support structure 38 and case 30, while the IPG PCB 42 is proximate to the top side.
FIG. 3 shows a lead connector subassembly 95 for the IPG 10, which includes the lead connectors 24, the header contacts 26, feedthrough pins 48, and a feedthrough 32. The feedthrough 32 acts as a hermetic means for passing via the feedthrough pins 48 electrode signals between the header contacts 26 (and ultimately electrodes 16) and the circuitry internal to the case 30 on the IPG PCB 42. Lead connector subassembly 95 can be formed by slipping the feedthrough pins 48 through the feedthrough 32, soldering one end of the feedthrough pins 48 to appropriate header contacts 26 in the lead connectors 24, and soldering or brazing the feedthrough pins 48 in the feedthrough 32 in a hermetic manner. Notice that the free ends of the feedthrough pins 48 are bent at 90 degrees relative to the feedthrough 32, which facilitates connection to the IPG PCB 42 as discussed subsequently. In this example, there are two rows of bent feedthrough pins 48, with the top row spaced by a distance d1, and the bottom row spaced by a distance d2, from a bottom surface of the feedthrough 32, the relevance of which will be explained later.
Some of the construction steps of the IPG 10 are shown in FIGS. 4A and 4B, and because these steps are disclosed in the '194 Application, they are only briefly summarized here. Construction begins by affixing a battery terminal face 57 of the battery 34 to the support structure 38, using double sided tape 58 for example. The combined support structure 38 and battery 34 is then placed in an assembly jig 94 as shown in cross section in FIG. 4B. Next, the lead connector subassembly 95 (FIG. 3) is positioned within the jig 94. Like the feedthrough pins 48 in the lead connector assembly 95, the battery terminals 46 are bent at 90 degrees relative to the battery terminal face 57, and so both the feedthrough pins 48 and battery terminals 46 are now pointing upward when placed in the jig 94. Next, the IPG PCB 42—preferably pre-fabricated with its electrical components—is affixed to the top side of the support structure 38. In this regard, IPG PCB 42 includes coil solder pin holes 50, battery terminal solder holes 52, feedthrough pin solder holes 54, and support structure mounting holes 56, which are respectively slipped over the upward-pointing coil pins 44 (in the support structure 38), feedthrough pins 48, battery terminals 46, and mounting pins 88 of the support structure 38. The coil pins 44, feedthrough pins 48, battery terminals 46 are then soldered to the coil solder pin holes 50, feedthrough pin solder holes 54, and battery terminal solder holes 52 respectively to electrically couple them to the IPG PCB 42. Thereafter, and as explained in the '194 Application, the resulting IPG subassembly 92 is then placed in its case 30, which is welded together and to the feedthrough 32, and the header 28 is then added to complete IPG 10's construction.
The inventors consider it desirable to electrically test the IPG PCB 42 before it is attached to the support structure 38 and electrically coupled to the battery 34 and feedthrough pins 48, and sealed within its case 30, and techniques are disclosed for doing so, which also involve improved designs and methods of constructing the IPG PCB 42.